- Pre-heat oven to 160°C/325°F/Gas Mark 3. Place the orange slices, onion slices, cloves, peppercorns and star anise in the bottom of a large roasting tin. Place a trivet on top of the oranges and onions. Sit the ham on the trivet and pour over boiled water into the roasting tin, about 4cm high.
- Tightly double layer the ham in foil. Place in the lower half of the oven and bake for 4 hours.
- Carefully remove from the oven. Place the ham onto a chopping board and discard the liquid. Peel off the skin leaving a thin layer of fat. Score all over in a diagonal pattern with a knife.
- In a saucepan melt the marmalade, sugar, mustard and allspice. Boil for 5 minutes until glossy and thick. Remove from the heat and leave to cool.
- Increase the oven temperature to 200°C/400°F/Gas Mark 6. Brush the ham with the glaze then put back in the oven for 20 minutes or until golden brown.